- ID:
- ivo://CDS.VizieR/J/A+A/606/A35
- Title:
- Barnard 1b-N and 1b-S 350GHz images
- Short Name:
- J/A+A/606/A35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The formation epoch of protostellar disks is debated because of the competing roles of rotation, turbulence, and magnetic fields in the early stages of low-mass star formation. Magnetohydrodynamics simulations of collapsing cores predict that rotationally supported disks may form in strongly magnetized cores through ambipolar diffusion or misalignment between the rotation axis and the magnetic field orientation. Detailed studies of individual sources are needed to cross check the theoretical predictions. We present 0.06-0.1arcsec resolution images at 350GHz toward B1b-N and B1b-S, which are young class 0 protostars, possibly first hydrostatic cores. The images have been obtained with ALMA, and we compare these data with magnetohydrodynamics simulations of a collapsing turbulent and magnetized core. The submillimeter continuum emission is spatially resolved by ALMA. Compact structures with optically thick 350GHz emission are detected toward both B1b-N and B1b-S, with 0.2 and 0.35arcsec radii (46 and 80au at the Perseus distance of 230pc), within a more extended envelope. The flux ratio between the compact structure and the envelope is lower in B1b-N than in B1b-S, in agreement with its earlier evolutionary status. The size and orientation of the compact structure are consistent with 0.2arcsec resolution 32GHz observations obtained with the Very Large Array as a part of the VANDAM survey, suggesting that grains have grown through coagulation. The morphology, temperature, and densities of the compact structures are consistent with those of disks formed in numerical simulations of collapsing cores. Moreover, the properties of B1b-N are consistent with those of a very young protostar, possibly a first hydrostatic core. These observations provide support for the early formation of disks around low-mass protostars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/79/77
- Title:
- Bell Lab. H I Survey - High Velocity Clouds
- Short Name:
- J/ApJS/79/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The sky north of declination -40 deg. was observed in the 21 cm line of atomic hydrogen with the FWHM = 2 deg. beam of the 20 foot horn reflector at AT&T Bell Laboratories, Crawford Hill. The survey covers a velocity range of 654 km/s centered on the Galactic standard of rest, with 5.3 km/s wide filters. This survey is distinguished by its sensitivity to low surface brightness features (antenna temperature about 50 mK) and relative freedom from sidelobe contamination. The high-velocity cloud list was extracted and catalogued automatically from the survey data.
- ID:
- ivo://CDS.VizieR/VIII/28
- Title:
- Bell Laboratories H I Survey
- Short Name:
- VIII/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The sky north of declination -40{deg} was observed in the 21cm line of atomic hydrogen with the FWHM=2{deg} beam of the 20 foot horn reflector at AT&T Bell Laboratories, Crawford Hill. The survey covers a velocity range of 654km/s centered on the Galactic standard of rest, with 5.3km/s wide filters. This survey is distinguished by its sensitivity to low surface brightness features (antenna temperature about 50mK) and relative freedom from sidelobe contamination. High-velocity clouds are extracted and catalogued automatically. The data are presented in declination zones in equatorial and polar coordinates, and as R.A. - velocity images.
- ID:
- ivo://CDS.VizieR/J/A+A/604/A52
- Title:
- B213 filament 150 and 260GHz emission maps
- Short Name:
- J/A+A/604/A52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The characterization of dust properties in the interstellar medium (ISM) is key for understanding the physics and chemistry of star formation. Mass estimates are crucial to determine gravitational collapse conditions for the birth of new stellar objects in molecular clouds. However, most of these estimates rely on dust models that need further observational constraints to capture the relevant parameters variations depending on the local environment: from clouds to prestellar and protostellar cores. We present results of a new study of dust emissivity changes based on millimeter (mm) continuum data obtained with the NIKA camera at the IRAM-30m telescope. Observing dust emission at 1.15mm and 2mm allows us to constrain the dust emissivity index, {beta}, in the Rayleigh-Jeans tail of the dust spectral energy distribution (SED) far from its peak emission, where the contribution of other parameters (i.e. dust temperature) is more important. Focusing on the Taurus molecular cloud, one of the most famous low-mass star-forming regions in the Gould Belt, we analyze the emission properties of several distinct objects in the B213 filament. This sub-parsec size region is of particular interest since it is characterized by the presence of a collection of evolutionary stages of early star formation: three prestellar cores, two Class-0/I protostellar cores and one Class-II object. We are therefore able to compare dust properties among a sequence of sources that likely derive from the same parent filament. By means of the ratio of the two NIKA channel-maps, we show that in the Rayleigh-Jeans approximation, {beta}_RJ_ varies among the objects: it decreases from prestellar cores ({beta}_RJ_~2) to protostellar cores ({beta}_RJ_~1) and the Class-II object ({beta}_RJ_~0). For one prestellar and two protostellar cores, we produce a robust study using available Herschel data to constrain the dust temperature of the sources. By using the Abel transform inversion technique we get accurate radial temperature profiles that allow us to obtain radial {beta} profiles. We find systematic spatial variations of {beta} in the protostellar cores that is not observed in the prestellar core. While in the former case {beta} decreases toward the center (with {beta} varying between 1 and 2), in the latter it remains constant ({beta}=2.4+/-0.3). Moreover, the dust emissivity index appears anticorrelated with the dust temperature. We discuss the implication of these results in terms of dust grain evolution between pre- and protostellar cores.
- ID:
- ivo://CDS.VizieR/J/ApJ/822/59
- Title:
- BGPS. XIV. Molecular cloud clumps GBT obs.
- Short Name:
- J/ApJ/822/59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We sort 4683 molecular clouds between 10{deg}<l<65{deg} from the Bolocam Galactic Plane Survey based on observational diagnostics of star formation activity: compact 70{mu}m sources, mid-IR color-selected YSOs, H_2_O and CH_3_OH masers, and UCHII regions. We also present a combined NH_3_-derived gas kinetic temperature and H_2_O maser catalog for 1788 clumps from our own GBT 100m observations and from the literature. We identify a subsample of 2223 (47.5%) starless clump candidates (SCCs), the largest and most robust sample identified from a blind survey to date. Distributions of flux density, flux concentration, solid angle, kinetic temperature, column density, radius, and mass show strong (>1dex) progressions when sorted by star formation indicator. The median SCC is marginally subvirial ({alpha}~0.7) with >75% of clumps with known distance being gravitationally bound ({alpha}<2). These samples show a statistically significant increase in the median clump mass of {Delta}M~170-370M_{sun}_ from the starless candidates to clumps associated with protostars. This trend could be due to (i) mass growth of the clumps at dM/dt~200-440M_{sun}_/Myr for an average freefall 0.8Myr timescale, (ii) a systematic factor of two increase in dust opacity from starless to protostellar phases, and/or (iii) a variation in the ratio of starless to protostellar clump lifetime that scales as ~M^-0.4^. By comparing to the observed number of CH_3_OH maser containing clumps, we estimate the phase lifetime of massive (M>10^3^M_{sun}_) starless clumps to be 0.37+/-0.08Myr (M/10^3^M_{sun}_)^-1^; the majority (M<450M_{sun}_) have phase lifetimes longer than their average freefall time.
- ID:
- ivo://CDS.VizieR/J/ApJ/727/114
- Title:
- BLAST 2005: a 10deg^2^ survey in Cygnus X
- Short Name:
- J/ApJ/727/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Cygnus X in a new multi-wavelength perspective based on an unbiased BLAST survey at 250, 350, and 500um, combined with rich data sets for this well-studied region. Our primary goal is to investigate the early stages of high-mass star formation. We have detected 184 compact sources in various stages of evolution across all three BLAST bands. From their well-constrained spectral energy distributions, we obtain the physical properties mass, surface density, bolometric luminosity, and dust temperature. Some of the bright sources reaching 40K contain well-known compact HII regions. We relate these to other sources at earlier stages of evolution via the energetics as deduced from their position in the luminosity-mass (L-M) diagram. The BLAST spectral coverage, near the peak of the spectral energy distribution of the dust, reveals fainter sources too cool (~10K) to be seen by earlier shorter-wavelength surveys like IRAS. We detect thermal emission from infrared dark clouds and investigate the phenomenon of cold "starless cores" more generally. Spitzer images of these cold sources often show stellar nurseries, but these potential sites for massive star formation are "starless" in the sense that to date there is no massive protostar in a vigorous accretion phase.
- ID:
- ivo://CDS.VizieR/J/ApJ/681/428
- Title:
- BLAST sources in Galactic plane survey
- Short Name:
- J/ApJ/681/428
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results from a new 250, 350, and 500um Galactic plane survey taken with the Balloon-borne Large-Aperture Submillimeter Telescope (BLAST) in 2005. This survey's primary goal is to identify and characterize high-mass protostellar objects (HMPOs). The region studied here covers 4{deg}^2^ near the open cluster NGC 6823 in the constellation Vulpecula (l=59{deg}). We find 60 compact sources (<60" diameter) detected simultaneously in all three bands. Their SEDs are constrained through BLAST, IRAS, Spitzer MIPS, and MSX photometry, with inferred dust temperatures spanning ~12-40K assuming a dust emissivity index {beta}=1.5. The luminosity-to-mass ratio, a distance-independ ent quantity, spans ~0.2-130L_{sun}_/M_{sun}_. Distances are estimated from coincident ^13^CO(1-0) velocities combined with a variety of other velocity and morphological data in the literature. In total, 49 sources are associated with a molecular cloud complex encompassing NGC 6823 (distance ~2.3kpc), 10 objects with the Perseus arm (~8.5kpc), and one object is probably in the outer Galaxy (~14kpc). Near NGC 6823, the inferred luminosities and masses of BLAST sources span ~40-10^4^L_{sun}_ and ~15-700M_{sun}_, respectively. The mass spectrum is compatible with molecular gas masses in other high-mass star-forming regions. Several luminous sources appear to be ultracompact H II regions powered by early B stars. However, many of the objects are cool, massive gravitationally bound clumps with no obvious internal radiation from a protostar, and hence excellent HMPO candidates.
- ID:
- ivo://CDS.VizieR/J/ApJ/707/1824
- Title:
- BLAST Vela sources
- Short Name:
- J/ApJ/707/1824
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present first results from an unbiased 50deg^2^ submillimeter Galactic survey at 250, 350, and 500um from the 2006 flight of the Balloon-borne Large Aperture Submillimeter Telescope. The map has resolution ranging from 36" to 60" in the three submillimeter bands spanning the thermal emission peak of cold starless cores. We determine the temperature, luminosity, and mass of more than 1000 compact sources in a range of evolutionary stages and an unbiased statistical characterization of the population. From comparison with C^18^O data, we find the dust opacity per gas mass, {kappa}r=0.16cm^2^/g at 250um, for cold clumps. We find that 2% of the mass of the molecular gas over this diverse region is in cores colder than 14K, and that the mass function for these cold cores is consistent with a power law with index {alpha}=-3.22+/-0.14 over the mass range 14M_{sun}_<M<80M_{sun}_.
69. Blobs in AT Cnc
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/739
- Title:
- Blobs in AT Cnc
- Short Name:
- J/MNRAS/465/739
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Z Cam-type dwarf nova AT Cancri (AT Cnc) displays a classical nova (CN) shell, demonstrating that mass transfer in cataclysmic binaries decreases substantially after a CN eruption. The hibernation scenario of cataclysmic binaries predicts such a decrease, on a time-scale of a few centuries. In order to measure the time since AT Cnc's last CN eruption, we have measured the radial velocities of a hundred clumps in its ejecta with SITELLE, Canada-France-Hawaii Telescope's recently commissioned imaging Fourier transform spectrometer. These range from -455 to +490km/s. Coupled with the known distance to AT Cnc of 460pc, the size of AT Cnc's shell, and a simple model of nova ejecta deceleration, we determine that the last CN eruption of this system occurred 330^+135^_-90_yr ago. This is the most rapid transition from a high mass-transfer rate, nova-like variable to a low mass-transfer rate, dwarf nova yet measured, and in accord with the hibernation scenario of cataclysmic binaries. We conclude by noting the similarity in the deduced outburst date (within a century of 1686 CE) of AT Cnc to a 'guest star' reported in the constellation Cancer by Korean observers in 1645 CE.
- ID:
- ivo://CDS.VizieR/J/A+A/597/A118
- Title:
- Bok globule BHR 160 radio lines spectra
- Short Name:
- J/A+A/597/A118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- BHR160 is a virtually unstudied cometary globule within the Sco OB4 association in Scorpius at a distance of 1600pc. It is part of a system of cometary clouds which face the luminous O star HD155806. BHR160 is special because it has an intense bright rim. We attempt to derive physical parameters for BHR160 and to understand its structure and the origin of its peculiar bright rim. BHR160 was mapped in the ^12^CO, ^13^CO and C^18^O (2-1) and (1-0) and CS (3-2) and (2-1) lines. These data, augmented with stellar photometry derived from the ESO VVV survey, were used to derive the mass and distribution of molecular material in BHR160 and its surroundings. Archival mid-infrared data from the WISE satellite was used to find IR excess stars in the globule and its neighbourhood.
